Abstract：To pinpoint genetic model of cucumber (Cucumis sativus) internode length and function mode of gene, and also to evaluate the genetic effect and heritability of major genes and minor genes, two culcmber parents with significantly different internode length, namely 'SJ57-h' (short internode, P1' hereinafter) and 'SJ11-1' (long internode, 'P2' hereinafter), were used to generate F1、B1、B2 and F2 populations for joint analysis. Mixed major-gene plus polygenes inheritance model were used to genetic law of internode length in both spring and autumn seasons. The results showed that the best fitted genetic model for cucumber internode size in both autumn and spring was D-0 model which internode length was controlled by one pair of additive-dominant-major genes plus additive-dominant-epitasis polygenes. Moreover, progeny internode length was closer to long-internode parent P2, namely, the progenies has long-internode parent heterosis. In spring, the major gene heritability of B1, B2 and F2 populations were estimated to be 68.5%, 36.2% and 56.3%, respectively, while the heritability of polygene was 0.6%, 17.1% and 0.6%, respectively. The variance of environment accounted for an average of 40.2% of the phenotypic variation among three generations. In autumn, heritability of the major gene among B1, B2 and F2 generations was estimated as 68.5%, 40.5%, 65.1%, while the heritability of polygene was 1.2%, 40.6% and 5.4%, respectively. Environment variance accounted for about 26.3% of the phenotypic variation. These results indicated that cucumber internode length was mainly controlled by a pair of major genes while the internode length was also obviously affected by environment factors in the B2 generation. Selection efficiency of major genes was relatively high in early generation of F2 and B1, whereas for selection efficiency of polygene was higher in B2 generation. Therefore, the trait of cucumber internode length was suitable for selection in early generation. The finding in the study will lay a theoretical foundation for breeding new cucumber vareties with improved plant architecture.
